Producing a semiconductor device based on a silicon semiconductor wafer may include a plurality of process sequences in which, for example, doped regions are formed in the wafer and metallization layers are formed on the wafer. During such processing undesired impurities such as metal atoms may end up in the wafer. Consequently, these impurities may unduly affect the operation of the finished semiconductor device. For example, in a power semiconductor device impurities may reduce the voltage blocking capability if they end up in a region of the device where in operation of the device high electric field strengths may occur.
A polysilicon layer formed on a surface of the wafer may getter those impurities, and may be removed after the impurity introducing processing so as to remove the impurities. However, for some wafer types a process for forming a polysilicon layer on the wafer surface is not available. There is therefore a need for an alternative impurity gettering.